Abstract: In a device for vertical adjustment of arm supports on chairs, especially wheel chairs, each arm support (1) is carried by a support pipe (2) longitudinally displaceably arranged in a bore (3') of a part (3) rigidly connected to the chair frame (1'), the support pipe (2) being lockable to the chair frame (1', 3) in its various positions of longitudinal displacement. It is aimed at providing a device of this kind wherein the height adjustment of the arm support occurs infinitely variably and controlled, and wherein the height-adjusting device is handy in use. For this purpose a longitudinally non-displacebable motion screw is rotationally supported within the support pipe (2), a lug (5) rigidly connected to the chair frame (1', 3) engaging said motion screw, the latter being adapted to cooperate with a manually releasable (8) locking device (9,10) which in the locking position prevents rotation of the motion screw (4).